coreos/etcd — pull request #1689 by yichengq (2014-11-12 00:27:57+00:00)
Title: raft: update unstable when calling stableTo with 0

It should update unstable in this case because it may happen that raft only writes entry
0 into stable storage.

for #1644
It makes the test rather slow because etcdserver keeps getting new ready with entry 0 as entries and writing it to disk before the leader syncs the whole log to the follower. It may happen 10000+ times when increasing cluster size from 3 to 6.